League Two side Coventry City also progressed as they beat MK Dons, while Watford were eliminated by fellow Premier League side Southampton.
In a day of few shocks, Wigan Athletic caused the biggest upset as they comfortably beat Premier League side West Ham. League Two side Coventry City also progressed as they beat MK Dons, while Watford were eliminated by fellow Premier League side Southampton.
There was no cupset in the early game as Leicester City comfortably beat Peterborough 5-1 at the ABAX Stadium as braces from both Kelechi Iheanacho and Fousseni Diabate along with a Wilfred Ndidi goal sent the Foxes into the fifth round.
In the biggest upset of the day, two goals from Will Grigg gave 2013 winners Wigan Athletic victory over West Ham at the DW Stadium. The Hammers fielded a weakened side, and will be without Arthur Masuaku for the next few games after the Frenchman was sent off for spitting.
League Two side Coventry City beat League One side MK Dons 1-0 at the Stadium MK, with a goal from Maxime Biamou sending the Sky Blues into the fifth round.
In the only all-Premier League affair Southampton beat Watford 1-0 at St.Mary's with birthday boy Jack Stephens scoring the only goal of the game.
In the all-Championship fixtures, Hull City eased passed Nottingham Forest with goals from Jarrod Bowen and Nouha Dicko giving the Tigers a 2-1 victory, while Sheffield United beat Preston 1-0 at Bramall Lane after Billy Sharp converted a late penalty.
Notts County held out for a replay as they drew 1-1 with Premier League side Swansea City at Meadow Lane. League One side Rochdale held on to draw 2-2 with Championship side Millwall at the Den, with the home side scoring very late on to safe their blushes.
In the other games Glenn Murray scored late on for Brighton as they beat Middlesbrough at the Riverside Stadium, while Huddersfield played out a 1-1 draw with Birmingham. Check out the 90min homepage for match reports and coverage of the rest of the day's games.